<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Test2</title>
    <script src="./js/vue.js"></script>
</head>

<body>
    <div class="app">
        <img src="./img/img.png" @mouseout="remake" @mouseover="change" alt="">
    </div>
    <script>
	var app = new Vue({
      	el:"#app",
    	data:{
        	opacity:1
      	},
          methods:{
                change(){
                    this.opacity = 0.6;
                },
                remake(){
                    this.opacity = 1;
                },
            }
        })
    </script>
</body>

</html>